A passive optical network (PON) consists of one or more optical line termination (OLT) systems (also referred to as OLTs), a number of optical network units (ONUs), and an optical distribution network (ODN) including fibers and splitters between the OLTs and the ONUs. Each OLT is a service provider node, and each ONU is a subscriber node. A PON is a widely-adopted architecture for economically delivering telecommunications services to individual subscribers or groups of subscribers. One common type of PON deployment is based on ITU-T G.984 (Gigabit-capable PON (GPON)).
In a GPON system, there is in general a one-to-many relationship between an OLT system and the ONUs. An example of an ONU is a Single Family Unit (SFU), which typically serves one house or apartment, or a Multi-Dueling Unit (MDU), which typically serves multiple houses or apartments.
Many GPON venders provide an OLT system and a portfolio of ONUs to address different market needs. Some ONU types are designed to provide both voice services (based on plain-old telephone service (POTS)) and data services; whereas other ONU types are designed to provide data services only, such as high speed internet access (HSIA), video and/or session initiation protocol (SIP) based services. Some ONU types are designed to include residential gateway capabilities; whereas other ONU types rely on an external third-party residential gateway. A typical leading GPON vendor may offer over twenty versions of ONU types to be supported by the same OLT system.
A typical OLT system when fully loaded may support up to tens of thousands of ONUs (e.g., 14×16×64=14,336 ONUs). To ensure that a fully loaded GPON OLT system meets the scalability, availability, reliability, performance and service quality requirements for different GPON markets where different ONU types are deployed, an equipment vendor often needs to test various traffic usage patterns and load conditions that are generated to/from the large number of ONUs. Using real field deployable ONUs in the lab (e.g., 14,336 ONUs) to test a fully loaded GPON OLT system becomes prohibitive with respect to the lab space, number of racks to stack the thousands of ONUs, number of cables, number of switches, human efforts to manage and operate the ONUs, and very high energy consumption.